Sculpting in 2.83 doesn't sculpt every verticies
see if there is any auto masking is active. if not then recalculate your normals.

6/19/2020 edit: it's a bug with triangle faces in blender 2.83 LTS. your workaround is to select your model go to edit mode and press f3 and search for tris to quads then try smooth sculpting. workaround worked on my side.